1. Field of the Invention
The present invention relates generally to a magnetic head and, more particularly, to an inductive/magnetoresistive (MR) composite head including a magnetoresistive (MR) head section laminated on a base. The present invention also relates to a method or process for producing the magnetic head.
2. Description of the Related Art
In conventional inductive/MR composite magnetic heads, it is known that an MR reading head section laminated on a base is frequently provided with an uneven end face facing away from the base, which is caused by a difference between the functionally required thickness of respective laminated layers of the MR head section. Such an uneven end face of the MR head section is apt to provide an uneven recording gap layer for an inductive recording head section formed above the MR head section in relation to the base. As a result, the linearity of the pattern of information written in a magnetic recording medium may be deteriorated, which can make it difficult to perform an optimum magnetic recording.
FIG. 10 shows in an enlarged schematic section an example of a laminated structure of a conventional inductive/MR composite magnetic head. The magnetic head includes a reading-side lower shield layer 102, a reading-side lower insulating layer 103, a magnetoresistive (MR) element layer 104, a hard magnetic element layer 105, a terminal layer 106, a reading-side upper insulating layer 107, a reading-side upper shield layer 108 also serving as a recording-side lower pole, a recording gap layer 109, a recording-side upper pole 110 and a protective layer 111, which are formed or laminated in this order on a base 101 by using a thin-film technique for producing semiconductors. In this arrangement, the MR element layer 104 has a thickness generally less than the total thickness of the adjacent hard magnetic element layer 105 plus terminal layer 106 as illustrated. Consequently, the upper end face of the reading head section, i.e., the upper surface of the reading-side upper shield layer 108, is unevenly formed, and thereby the evenness of the recording gap layer 109 of a recording head section is lost.
The thickness of each layer of the composite magnetic head is determined to be in a certain range functionally required for the respective layer. For example, the thickness of the MR element layer 104 is determined in a range required for obtaining a desired is magnetoresistive effect, the thickness of the hard magnetic element layer 105 is determined in a range required for obtaining a desired magnetic domain adjusting function for the MR element layer 104, and the thickness of the terminal layer 106 is determined in a range required for obtaining a desired current supply and signal transmission function for the MR element layer 104. Therefore, it is not preferred, in consideration of the performance of the magnetic head, to simply equalize the thickness of the MR element layer 104 with the total thickness of the hard magnetic element layer 105 plus terminal layer 106, in order to flatten the recording gap layer 109. In this situation, it is required to even the upper end face of the reading head section without changing the respective thickness of the MR element layer 104, the hard magnetic element layer 105 and the terminal layer 106 and, thereby, to flatten the recording gap layer 109.
Japanese Unexamined Patent Publication (Kokai) No. 9-81919 (JP-A-9-81919) discloses a method for producing a thin-film magnetic head which can even a recording gap layer without changing the respective thickness of an MR element layer, a hard magnetic element layer and a terminal layer. According to this method, after the MR element layer is formed and before the hard magnetic element layer is laminated, a thin film layer, of which a thickness corresponds to the difference between the thickness of the MR element layer and the total thickness of the hard magnetic element layer plus terminal layer, is laminated on the MR element layer. After that, the hard magnetic element layer and the terminal layer are laminated adjacent to the MR element layer and the thin film layer, so that the upper surface of the thin film layer and the upper surface of the terminal layer are located generally in an identical plane or level. Consequently, the recording gap layer formed above the thin film layer is substantially flattened.
In this prior-art method, it is possible to flatten the recording gap layer, but it is necessary to perform an additional step for forming the thin film layer on the MR element layer in the laminating process of the magnetic head. The introduction of the additional step may increase the production time and cost of the magnetic head. Also, the thin film layer formed on the MR element layer increases a reading gap dimension, i.e., the distance between the reading-side lower and upper shield layers arranged at respective sides of the MR element layer. The reading gap dimension normally affects directly the reading signal characteristic of the magnetic head. Therefore, the above method may deteriorate the reading signal characteristic.
Instead of the above method, it may be possible to even the upper surface of the reading-side upper insulating layer or of the reading-side upper shielding layer by a mechanical or chemical process for removing a material during the laminating process. However, this material removing process is also an additional step introduced into the laminating process, and thus may increase the production time and cost of the magnetic head. In particular, when the upper surface of the reading-side upper insulating layer is flattened by the material removing process, it is preferred to previously increase the thickness of the reading-side upper insulating layer so as to prevent the step coverage function thereof at a stepped portion formed between the MR element layer and the terminal layer from being deteriorated. As a result, the reading gap dimension is increased in the same manner as the above method, and thus the reading signal characteristic may be deteriorated.